Clamping device

ABSTRACT

A clamping device ( 1, 25, 35 ) for releasably clamping an insertion member ( 9, 27, 38 ) with a shank portion, the clamping device comprising a clamping member having an insertion bore ( 11, 26, 40 ) formed by the union of an access bore portion ( 19 A,  31 A,  41 A) and a gripping bore portion ( 19 B,  31 B,  41 B) for the free sliding insertion into and withdrawal from the shank portion in respect of the access bore portion and its clamping by a clamping surface of the gripping bore portion on its forced displacement thereinto from the access bore portion, the access and gripping bore portions having longitudinal axes ( 20 A,  20 B;  32 A,  32 B;  43 A,  43 B) spaced apart at least along a portion thereof.

FIELD OF THE INVENTION

The invention relates to clamping devices for releasably clamping aninsertion member.

BACKGROUND OF THE INVENTION

A common application of clamping devices is the releasable clamping of acutting tool (constituting an insertion member) in a toolholder(constituting a clamping device). In JP Unexamined Patent Publication7-9212, there is illustrated and described a side lock toolholder havingan insertion bore formed by the union of an access bore portion and agripping bore portion, the access bore portion and the gripping boreportion sharing a common longitudinal axis and respectively having, aradius r′ and a radius r where r′>R>r and R is the radius of a cuttingtool's right circular cylindrical shank. The access bore portion extendsover an arc angle of almost 180° such that the cutting tool is freelyslidingly insertable thereinto and withdrawable therefrom, the cuttingtool being forcibly displaceable from the access bore portion to thegripping bore portion. Such a toolholder has a disadvantage that the arcangle of the gripping bore portion is less than 180° which reduces thegripping capability of the gripping bore portion which impairs stabilityduring a cutting operation.

SUMMARY OF THE INVENTION

In accordance with the present invention, there is provided a clampingdevice for releasably clamping an insertion member, the clamping devicecomprising a clamping member having an insertion bore formed by theunion of an access bore portion and a gripping bore portion for the freesliding insertion into and withdrawal from of the shank portion inrespect of said access bore portion and its clamping by a clampingsurface of said gripping bore portion on its forced displacementthereinto from said access bore portion

characterized in

said access and gripping bore portions having longitudinal axes spacedapart at least along a portion thereof.

In accordance with a first mode of implementation of the presentinvention, an insertion bore can be formed by the union of a pair ofcircular cross section access and gripping bore portions respectivelyhaving longitudinal axes which are parallel and offset one from anotherwhereby an insertion member is sideways forcibly displaced from itsaccess bore portion to its gripping bore portion. Preferably, an accessbore portion has a right circular cylindrical shape whilst a grippingbore portion can have either a right circular cylindrical shape or aright circular frusto-conical shape.

In accordance with a second mode of implementation of the presentinvention, an insertion bore can be formed by the union of a pair ofcircular cross section access and gripping bore portions respectivelyhaving longitudinal axes which are intersecting whereby an insertionmember is pivotally forcibly displaced from its access bore portion intoits gripping bore portion. Preferably, an access bore portion has aninclined circular cylindrical shape whilst an gripping bore portion hasa right circular cylindrical shape.

In both modes of implementation, the access bore portion has a diameterD₁ whose minimum value is greater than the diameter D₀ of an insertionmembers shank portion whilst the gripping bore portion has a maximumvalue D₂ which is less than D₀. In addition, in the former mode ofimplementation, the two longitudinal axes are spaced apart at a distanceD₃ whilst in the latter mode of implementation, the two longitudinalaxes are inclined at an inclination angle γ.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and how it is used, preferredembodiments will now be described by way of non-limiting examples only,with reference to the accompanying drawing in which:

FIG. 1 is a partially cut-away perspective view of a toolholder clampfixture for releasably clamping a toolholder;

FIGS. 2 and 3 are respectively transverse cross sectional views of thetoolholder clamp fixture along a line I—I in FIG. 1 showing a toolholderin its initial insertion and subsequent clamped positions;

FIG. 4 is a perspective view of a toolholder for releasably clamping acutting tool;

FIG. 5 is a top view of the toolholder of FIG. 4;

FIG. 6 is a longitudinal cross sectional view of the toolholder along aline II—II in FIG. 4;

FIG. 7 is a perspective view of a part of a toolholder and a wrench forreleasing and tightening a clamping nut of the toolholder;

FIG. 8 is a perspective view of the wrench of FIG. 7;

FIGS. 9A-9C are respectively longitudinal cross sectional views of thewrench of FIG. 7 along lines III—III, IV—IV and V—V respectively in FIG.8;

FIGS. 10A and 10B are respectively perspective and longitudinal crosssectional views of the wrench and toolholder of FIG. 7 with thetoolholder in its initial insertion position;

FIGS. 11A and 11B are respectively perspective and longitudinal crosssectional views of the wrench and toolholder of FIG. 7 with thetoolholder in its subsequent clamped position; and

FIGS. 12A and 12B are longitudinal cross sectional views of a side locktoolholder taken along a line II—II of FIG. 4 for radially and axiallyclamping a toolholder.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In FIGS. 1-3, a toolholder clamp fixture 1 (constituting a clampingdevice) includes an L-shaped mounting fame 2 having a horizontalmounting member 3 adapted for mounting the toolholder clamp fixture 1 ona workbench 4 by means of a pair of mounting screws 5A and 5B and anupright support 7 on which is mounted a toolholder clamp 8. Thetoolholder clamp 8 is adapted for releasably clamping a toolholder 9(constituting an insertion member) which can be any one of a wide rangeof different types of toolholders, for example, an HSK-type toolholder,having a right circular cylindrical shank portion 10 of diameter D₀. Thetoolholder clamp 8 has an insertion bore 11 formed with an intermediatesupport shoulder 13 on which rests a lower abutment surface 14 of theshank portion 10. The toolholder 9 is secured in an upper holdingportion 15 of the insertion bore 11 atop the support shoulder 13 bymeans of a securing device 16 having a sleeve 17 for bearing against theshank portion 10.

As shown in FIGS. 2 and 3, the upper holding portion 15 is formed by theunion of right circular cylindrical access and gripping bore portions19A and 19B respectively adjacent and remote from the securing device16. The access and gripping bore portions 19A and 19B respectively havediameters D₁ and D₂ and parallel longitudinal axes 20A and 20B offsetone from the other by an offset distance D₃. The inner surfaces of theaccess and gripping bore portions 19A and 19B intersect at junctionlines (not shown) delimiting a generally semi cylindrical clampingsurface 21 of the gripping bore portion 19B having an arc angle greaterthan 180°.

In use, the securing device 16 is initially screwed outwardly from thetoolholder clamp 8 such that the toolholders shank portion 10 can bereadily slidingly inserted into its access bore portion 19A (see FIG.2). Thereafter, the securing device 16 is screwed into the toolholderclamp 8 such that its sleeve 17 presses against the toolholders shankportion 10 whereby it is clampingly received by the gripping boreportion 19B on its forced expansion. Once clamped, a new cutting toolcan be clamped into the toolholders cutting tool receiving bore 22 or,alternatively, a worn cutting tool can be replaced. Finally, thesecuring device 16 is screwed outwardly and the toolholder 9 is manuallyforced back into the access bore portion 19A from which it can bereadily slidingly withdrawn. Passage back into the access bore portion19A is typically evidenced by a click as the toolholder 9 passes pastthe junction lines between the access and gripping bore portions 19A and19B.

With reference now to FIGS. 4-6, there is shown a side lock toolholder25 (constituting a clamping device) of a two-piece construction with anouter tubular portion 25A and an inner tubular core portion 25B formedwith an insertion bore 26 for releasably clamping a cutting tool 27(constituting an insertion member) having a right circular cylindricalshank 28 by means of a transversely directed clamping screw 29 bearingthereagainst. The portions 25A and 25B are made of different materialsso as to substantially dampen tool chatter, for example, the portion 25Acan be made from steel whilst the portion 25B can be made from castiron.

The insertion bore 26 is similar to the insertion bore 15 in that it isformed by the union of an access bore portion 31A and a gripping boreportion 31B respectively having longitudinal axes 32A and 32B paralleland offset to one another (see FIGS. 5 and 6). However, since theinsertion bore 26 is closed at one end, its open end is more susceptibleto forced expansion than its closed end such that if gripping boreportion 31B is cylindrical in shape, then the gripping force as impartedthereby would not be uniform. In order to ensure that the right circularcylindrical shank 28 is gripped uniformly along the entire length of thegripping bore portion 31B, the gripping bore portion 31B has, instead ofa cylindrical shape, a right circular frusto-conical shape. Thecross-section of the gripping bore portion 31B, taken perpendicular tothe axis 32B, is greater at its closed end than at its open end. Theinner surfaces of the respective access and gripping bore portions 31Aand 31B, intersect at junction fines 33A and 33B. By means of thefrusto-conical shape described above, the same gripping capability isachieved along the entire length of the gripping bore portion, such thatits clamping surface 33 has an equal arc angle at both ends when thecutting tool 27 is clamped in the gripping bore portion 31B.

The use of the toolholder 25 for clamping a cutting tool 27 is similarto that of the toolholder clamp fixture 1. By way of example, atoolholder 25 for use with a cutting tool 27 having a shank diameterD₀=20.00 mm has an insertion bore 26 defined by the following insertionbore triplet D₁=20.07 mm, D₂=19.985 mm to D₂=19.995 mm, D₃=1 mm. In thiscase, when the cutting tool 27 is clamped in the gripping bore portion31B, the arc angle of the clamping surface 33 is about 181° at both endsof the gripping bore portion 31B.

With reference now to FIGS. 7-11, a wrench 35 (constituting a clampingdevice) includes an elongated arm 36 terminating in a wrench head 37adapted for releasing and tightening a right circular cylindricalclamping nut 39 (constituting a shank portion) of diameter D₀ of atoolholder 38 (constituting an insertion member). The wrench head 37 hasan insertion bore 40 formed by the union of a right circular cylindricalgripping bore portion 41B of diameter D₂ and an inclined circularcylindrical access bore portion 41A of diameter D₁ whereby theirrespective longitudinal axes 43B and 43A define an inclination angle γ(see FIGS. 8 and 9A) therebetween. The longitudinal axes 43A and 43Bintersect at the midpoints of the respective access bore portion 41A andthe gripping bore portion 41B such that their surfaces intersect at apair of crescent shaped junction lines 44A and 44B thereby defining apair of crescent shaped surfaces 45A and 45B of the access bore portion41A.

In use, the wrench 35 is initially inclined relative to a verticallyheld toolholder 38 so that it can be slided thereonto so that theclamping nut 39 is nested within the access bore portion 41A (see FIGS.10A and 10B). Thereafter, the wrench 35 is rotated clockwise, as shownby the dashed arrow in FIG. 10B, relative to the toollholder 38 toforcibly insert the clamping nut 39 into the gripping bore portion 41B,thereby clamping the wrench 35 on the clamping nut 39. In this position,the wrench 35 is rotated around the axis 43B thus releasing the clampingnut 39 (see FIGS. 11A and 11B). A worn cutting tool can then be replacedby a new cutting tool and the clamping nut 39 is tightened by a counterdirection rotation of the wrench 35 relative to the toolholder 38 aroundthe axis 43B. Upon re-tightening the clamping nut 39, the wrench 35 iscounter clockwise rotated in a direction opposite to that shown by thedashed arrow in FIG. 10B. As a result, the contact between the clampingnut 39 and the gripping bore portion 41B is released and the wrench 35can be upwardly removed from the toolholder 38.

Various modifications and changes may be made in the configurationdescribed above that come within the spirit of the invention. Theinvention embraces all such changes and modifications coming within thescope of the appended claims. For example, the longitudinal axes of aninsertion bore's access bore portion and gripping bore portion do nothave to lie on a single plane as long as an insertion member can bedisplaced therebetween.

In addition, as shown in FIGS. 12A and 12B, a side lock toolholder 25 isused with a cutting tool 42 formed with a recess 42A having an inclinedsurface engaged by the toolholder's clamping screw 29 for simultaneouslyforcibly displacing the cutting tool 42 from its access bore portion 31Ato its gripping bore portion 31B, by means of the radial componentF_(ST) of the screw's clamping force F_(S), whilst axially urging thecutting tool 42 against the toolholder's leading abutment surface 30, bymeans of the axial component F_(sa) of the screw's clamping force F_(S),thereby securely clamping the cutting tool 42. The recess 42A can beeither relatively shallow (see FIG. 12A) whereby F₂>F₁ suitable, forexample, for a turning cutting tool or, relatively deep (see FIG. 12B)whereby F₂=F₁ suitable, for example, for a drilling or a milling cuttingtool, where F₁ and F₂ are the axial abutting forces.

What is claimed is:
 1. A tool assembly comprising: a tool holdercomprising a shank portion having a diameter D0 along a first portionthereof; and a clamping member having an insertion bore formed by theunion of an access bore portion and a gripping bore portion, wherein:said access bore portion has a circular cross section with diameter D1in a transverse cross sectional view of said clamping member; saidgripping bore portion has a circular cross section with diameter D2 insaid transverse cross sectional view of said clamping member, thegripping bore portion having an arcuate clamping surface with an arcangle greater than 180°; said access bore portion and said gripping boreportion have longitudinal axes spaced apart at least along a portionthereof; and the tool assembly is movable between a disassembledposition in which the tool holder's shank portion and the arcuateclamping surface are separated, and an assembled position in which thetool holder's shank portion is in abutment with the arcuate clampingsurface.
 2. The tool assembly according to claim 1, wherein D1>D0>D2. 3.The tool assembly according to claim 1, wherein said longitudinal axesdefine a single plane.
 4. The tool assembly according to claim 3,wherein said access and gripping bore portions each have a rightcircular shape.
 5. The tool assembly according to claim 3, wherein saidaccess bore portion has right circular cylindrical shape and saidgripping bore portion has right circular frusto-conical shape.
 6. Thetool assembly according to claim 1, wherein said longitudinal axes areinclined to another one.
 7. The tool assembly according to claim 6,wherein said access bore portion has an inclined circular cylindricalshape and said gripping bore portion has a right circular cylindricalshape.
 8. The tool assembly according to claim 1, wherein said clampingmember includes an outer tubular portion and an inner tubular coreportion formed with said insertion bore and wherein said outer and innerportions are made from different materials.
 9. The tool assemblyaccording to claim 1, further comprising a leading abutment surface foraxially supporting the tool holder, and a clamping screw for engaging aninclined surface of the tool holder for simultaneously forciblydisplacing the tool holder from said access bore portion to saidgripping bore portion and axially urging the tool holder against saidleading abutment surface.
 10. A tool assembly comprising: a tool holdercomprising a shank portion having a diameter D0 along a first portionthereof; and a clamping member having an insertion bore formed by theunion of an access bore portion and a gripping bore portion, wherein:said access bore portion has a circular cross section with diameter D1in a transverse cross sectional view of said clamping member; saidgripping bore portion has a circular cross section with diameter D2 insaid transverse cross sectional view of said clamping member, thegripping bore portion having an arcuate clamping surface; said accessbore portion and said gripping bore portion have longitudinal axesspaced apart at least along a portion thereof; D1>D0>D2; the toolassembly is movable between a disassembled position in which the toolholder's arcuate shank portion and the arcuate clamping surface areseparated, and an assembled position in which the tool holder's arcuateshank portion is in abutment with the arcuate clamping surface, uponforced displacement of the tool holder's arcuate shank portion from theaccess bore portion into the gripping bore portion; and wherein saidclamping member includes an outer tubular portion and an inner tubularcore portion formed with said insertion bore and wherein said outer andinner portions are made from different materials.
 11. The tool assemblyaccording to claim 10, wherein the clamping surface has an arc anglegreater than 180°.
 12. The tool assembly according to claim 10, whereinsaid longitudinal axes define a single plane.
 13. The tool assemblyaccording to claim 12, wherein said access and gripping bore portionseach have a right circular shape.
 14. The tool assembly according toclaim 10, further comprising a leading abutment surface for axiallysupporting the tool holder, and a clamping screw for engaging aninclined surface of the tool holder for simultaneously forciblydisplacing the tool holder from said access bore portion to saidgripping bore portion and axially urging the tool holder against saidleading abutment surface.
 15. A tool assembly comprising: a tool holdercomprising a shank portion having a diameter D0 along a first portionthereof; and a clamping member having an insertion bore formed by theunion of an access bore portion and a gripping bore portion, wherein:said access bore portion has a circular cross section with diameter D1in a transverse cross sectional view of said clamping member; saidgripping bore portion has a circular cross section with diameter D2 insaid transverse cross sectional view of said clamping member, thegripping bore portion having an arcuate clamping surface; said accessbore portion and said gripping bore portion have longitudinal axesspaced apart at least along a portion thereof; D1>D0>D2; the toolassembly is movable between a disassembled position in which the toolholder's arcuate shank portion and the arcuate clamping surface areseparated, and an assembled position in which the tool holder's arcuateshank portion is in abutment with the arcuate clamping surface, uponforced displacement of the tool holder's arcuate shank portion from theaccess bore portion into the gripping bore portion; said longitudinalaxes define a single plane; and said access bore portion has rightcircular cylindrical shape and said gripping bore portion has rightcircular frusto-conical shape.
 16. A tool assembly comprising: a toolholder comprising a shank portion having a diameter D0 along a firstportion thereof; and a clamping member having an insertion bore formedby the union of an access bore portion and a gripping bore portion,wherein: said access bore portion has a circular cross section withdiameter D1 in a transverse cross sectional view of said clampingmember; said gripping bore portion has a circular cross section withdiameter D2 in said transverse cross sectional view of said clampingmember, the gripping bore portion having an arcuate clamping surface;said access bore portion and said gripping bore portion havelongitudinal axes spaced apart at least along a portion thereof;D1>D0>D2; the tool assembly is-movable between a disassembled positionin which the tool holder's arcuate shank portion and the arcuateclamping surface are separated, and an assembled position in which thetool holder's arcuate shank portion is in abutment with the arcuateclamping surface, upon forced displacement of the tool holder's arcuateshank portion from the access bore portion into the gripping boreportion; and said longitudinal axes are inclined to one another.
 17. Thetool assembly according to claim 16, said access bore portion has aninclined circular cylindrical shape and said gripping bore portion has aright circular cylindrical shape.
 18. A tool assembly comprising: aclamping member having an insertion bore formed by the union of anaccess bore portion and a gripping bore portion, wherein: said accessbore portion has a circular cross section with diameter D1 in atransverse cross sectional view of said clamping member; said grippingbore portion has a circular cross section with diameter D2 in saidtransverse cross sectional view of said clamping member, the grippingbore portion having an arcuate clamping surface having an arc anglegreater than 180°; and D1>D2.
 19. The tool assembly according to claim18, further comprising: a tool holder having a shank portion having adiameter D0 with D1>D0>D2; and wherein the tool assembly is movablebetween a disassembled position in which the tool holder's shank portionand the arcuate clamping surface are separated, and an assembledposition in which tool holder's shank portion is in abutment with thearcuate clamping surface, upon forced displacement of the tool holder'sshank portion from the access bore portion into the gripping boreportion.